Problems with the Pitchi Poy Rig
Make sure that when you create the parent child relationship the bones are within the mesh and the bones are selected last.



Make sure that all bones have their deform check box ... checked active.

In the modifiers pane inspect the armature modifier.  The enable eye icon should be active.  It can be turned off and on.  If is turned off it will have no effect.



You can also delete the armature modifier and parent it again.  Make sure to view the armature and the mesh from 3 angles top, front and side to make sure the alignment is correct.  If you have not done much weight painting do not hesitate to delete the armature modifier and parent again.